diff --git a/service-t/src/com/android/metrics/NetworkStatsMetricsLogger.java b/service-t/src/com/android/metrics/NetworkStatsMetricsLogger.java
index 2cf49ba..4f5d6be 100644
--- a/service-t/src/com/android/metrics/NetworkStatsMetricsLogger.java
+++ b/service-t/src/com/android/metrics/NetworkStatsMetricsLogger.java
@@ -29,15 +29,19 @@
 import static com.android.server.ConnectivityStatsLog.NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_XT;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.net.NetworkStatsCollection;
 import android.net.NetworkStatsHistory;
+import android.util.Pair;
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.server.ConnectivityStatsLog;
 
+import java.io.File;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.regex.Pattern;
 
 /**
  * Helper class to log NetworkStats related metrics.
@@ -95,10 +99,46 @@
     }
 
     /**
+     * Get file count and total byte count for the given directory and prefix.
+     *
+     * @return File count and total byte count as a pair, or 0s if met errors.
+     */
+    private static Pair<Integer, Integer> getStatsFilesAttributes(
+            @Nullable File statsDir, @NonNull String prefix) {
+        if (statsDir == null) return new Pair<>(0, 0);
+
+        // Only counts the matching files.
+        // The files are named in the following format:
+        //   <prefix>.<startTimestamp>-[<endTimestamp>]
+        //   e.g. uid_tag.12345-
+        // See FileRotator#FileInfo for more detail.
+        final Pattern pattern = Pattern.compile("^" + prefix + "\\.[0-9]+-[0-9]*$");
+
+        // Ensure that base path exists.
+        statsDir.mkdirs();
+
+        int totalFiles = 0;
+        int totalBytes = 0;
+        for (String name : emptyIfNull(statsDir.list())) {
+            if (!pattern.matcher(name).matches()) continue;
+
+            totalFiles++;
+            // Cast to int is safe since stats persistent files are several MBs in total.
+            totalBytes += (int) (new File(statsDir, name).length());
+
+        }
+        return new Pair<>(totalFiles, totalBytes);
+    }
+
+    private static String [] emptyIfNull(@Nullable String [] array) {
+        return (array == null) ? new String[0] : array;
+    }
+
+    /**
      * Log statistics from the NetworkStatsRecorder file reading process into statsd.
      */
     public void logRecorderFileReading(@NonNull String prefix, int readLatencyMillis,
-                                              @NonNull NetworkStatsCollection collection) {
+            @Nullable File statsDir, @NonNull NetworkStatsCollection collection) {
         final Set<Integer> uids = new HashSet<>();
         final Map<NetworkStatsCollection.Key, NetworkStatsHistory> entries =
                 collection.getEntries();
@@ -112,12 +152,12 @@
             totalHistorySize += history.size();
         }
 
-        // TODO: Fill file characteristics.
+        final Pair<Integer, Integer> fileAttributes = getStatsFilesAttributes(statsDir, prefix);
         mDeps.writeRecorderFileReadingStats(prefixToRecorderType(prefix),
                 mReadIndex++,
                 readLatencyMillis,
-                0 /* fileCount */,
-                0 /* totalFileSize */,
+                fileAttributes.first /* fileCount */,
+                fileAttributes.second /* totalFileSize */,
                 entries.size(),
                 uids.size(),
                 totalHistorySize);
diff --git a/service-t/src/com/android/server/net/NetworkStatsRecorder.java b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
index 456a212..0fe13f0 100644
--- a/service-t/src/com/android/server/net/NetworkStatsRecorder.java
+++ b/service-t/src/com/android/server/net/NetworkStatsRecorder.java
@@ -22,6 +22,7 @@
 import static android.text.format.DateUtils.YEAR_IN_MILLIS;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.net.NetworkIdentitySet;
 import android.net.NetworkStats;
 import android.net.NetworkStats.NonMonotonicObserver;
@@ -45,6 +46,7 @@
 import libcore.io.IoUtils;
 
 import java.io.ByteArrayOutputStream;
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -93,6 +95,8 @@
 
     private WeakReference<NetworkStatsCollection> mComplete;
     private final NetworkStatsMetricsLogger mMetricsLogger = new NetworkStatsMetricsLogger();
+    @Nullable
+    private final File mStatsDir;
 
     /**
      * Non-persisted recorder, with only one bucket. Used by {@link NetworkStatsObservers}.
@@ -114,6 +118,7 @@
         mSinceBoot = new NetworkStatsCollection(mBucketDuration);
 
         mPendingRewriter = null;
+        mStatsDir = null;
     }
 
     /**
@@ -121,7 +126,7 @@
      */
     public NetworkStatsRecorder(FileRotator rotator, NonMonotonicObserver<String> observer,
             DropBoxManager dropBox, String cookie, long bucketDuration, boolean onlyTags,
-            boolean wipeOnError, boolean useFastDataInput) {
+            boolean wipeOnError, boolean useFastDataInput, @Nullable File statsDir) {
         mRotator = Objects.requireNonNull(rotator, "missing FileRotator");
         mObserver = Objects.requireNonNull(observer, "missing NonMonotonicObserver");
         mDropBox = Objects.requireNonNull(dropBox, "missing DropBoxManager");
@@ -136,6 +141,7 @@
         mSinceBoot = new NetworkStatsCollection(bucketDuration);
 
         mPendingRewriter = new CombiningRewriter(mPending);
+        mStatsDir = statsDir;
     }
 
     public void setPersistThreshold(long thresholdBytes) {
@@ -192,7 +198,8 @@
             // For legacy recorders which are used for data integrity check, which
             // have wipeOnError flag unset, skip reporting metrics.
             if (mWipeOnError) {
-                mMetricsLogger.logRecorderFileReading(mCookie, (int) (readEnd - readStart), res);
+                mMetricsLogger.logRecorderFileReading(mCookie, (int) (readEnd - readStart),
+                        mStatsDir, res);
             }
         }
         return res;
diff --git a/service-t/src/com/android/server/net/NetworkStatsService.java b/service-t/src/com/android/server/net/NetworkStatsService.java
index ad83e7f..ce7fd7b 100644
--- a/service-t/src/com/android/server/net/NetworkStatsService.java
+++ b/service-t/src/com/android/server/net/NetworkStatsService.java
@@ -969,7 +969,7 @@
         return new NetworkStatsRecorder(new FileRotator(
                 baseDir, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
                 mNonMonotonicObserver, dropBox, prefix, config.bucketDuration, includeTags,
-                wipeOnError, false /* useFastDataInput */);
+                wipeOnError, false /* useFastDataInput */, baseDir);
     }
 
     @GuardedBy("mStatsLock")
diff --git a/tests/benchmark/src/android/net/netstats/benchmarktests/NetworkStatsTest.kt b/tests/benchmark/src/android/net/netstats/benchmarktests/NetworkStatsTest.kt
index c3ea9f4..57602f1 100644
--- a/tests/benchmark/src/android/net/netstats/benchmarktests/NetworkStatsTest.kt
+++ b/tests/benchmark/src/android/net/netstats/benchmarktests/NetworkStatsTest.kt
@@ -156,7 +156,8 @@
                 UID_COLLECTION_BUCKET_DURATION_MS,
                 false /* includeTags */,
                 false /* wipeOnError */,
-                useFastDataInput /* useFastDataInput */
+                useFastDataInput /* useFastDataInput */,
+                it
             )
             recorder.orLoadCompleteLocked
         }
diff --git a/tests/unit/java/android/net/NetworkStatsRecorderTest.java b/tests/unit/java/android/net/NetworkStatsRecorderTest.java
index 9ec9a79..afed227 100644
--- a/tests/unit/java/android/net/NetworkStatsRecorderTest.java
+++ b/tests/unit/java/android/net/NetworkStatsRecorderTest.java
@@ -20,10 +20,12 @@
 import static android.net.NetworkStats.SET_FOREGROUND;
 import static android.net.NetworkStats.TAG_NONE;
 import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_UID;
+import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_UID_TAG;
 import static android.net.netstats.NetworkStatsDataMigrationUtils.PREFIX_XT;
 import static android.text.format.DateUtils.HOUR_IN_MILLIS;
 
 import static com.android.server.ConnectivityStatsLog.NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_UID;
+import static com.android.server.ConnectivityStatsLog.NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_UIDTAG;
 import static com.android.server.ConnectivityStatsLog.NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_XT;
 import static com.android.testutils.DevSdkIgnoreRuleKt.SC_V2;
 
@@ -36,6 +38,7 @@
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
+import android.annotation.NonNull;
 import android.net.NetworkIdentity;
 import android.net.NetworkIdentitySet;
 import android.net.NetworkStats;
@@ -49,12 +52,17 @@
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRunner;
 
+import libcore.testing.io.TestIoUtils;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 
 @RunWith(DevSdkIgnoreRunner.class)
@@ -78,7 +86,7 @@
     private NetworkStatsRecorder buildRecorder(FileRotator rotator, boolean wipeOnError) {
         return new NetworkStatsRecorder(rotator, mObserver, mDropBox, TEST_PREFIX,
                 HOUR_IN_MILLIS, false /* includeTags */, wipeOnError,
-                false /* useFastDataInput */);
+                false /* useFastDataInput */, null /* baseDir */);
     }
 
     @Test
@@ -106,7 +114,7 @@
         final NetworkStatsMetricsLogger.Dependencies deps =
                 mock(NetworkStatsMetricsLogger.Dependencies.class);
         final NetworkStatsMetricsLogger logger = new NetworkStatsMetricsLogger(deps);
-        logger.logRecorderFileReading(PREFIX_XT, 888, collection);
+        logger.logRecorderFileReading(PREFIX_XT, 888, null /* statsDir */, collection);
         verify(deps).writeRecorderFileReadingStats(
                 NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_XT,
                 1 /* readIndex */,
@@ -119,7 +127,7 @@
         );
 
         // Write second time, verify the index increases.
-        logger.logRecorderFileReading(PREFIX_XT, 567, collection);
+        logger.logRecorderFileReading(PREFIX_XT, 567, null /* statsDir */, collection);
         verify(deps).writeRecorderFileReadingStats(
                 NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_XT,
                 2 /* readIndex */,
@@ -148,7 +156,7 @@
         final NetworkStatsMetricsLogger.Dependencies deps =
                 mock(NetworkStatsMetricsLogger.Dependencies.class);
         final NetworkStatsMetricsLogger logger = new NetworkStatsMetricsLogger(deps);
-        logger.logRecorderFileReading(PREFIX_UID, 123, collection);
+        logger.logRecorderFileReading(PREFIX_UID, 123, null /* statsDir */, collection);
         verify(deps).writeRecorderFileReadingStats(
                 NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_UID,
                 1 /* readIndex */,
@@ -160,4 +168,41 @@
                 5 /* totalHistorySize */
         );
     }
+
+    @Test
+    public void testFileReadingMetrics_fileAttributes() throws IOException {
+        final NetworkStatsCollection collection = new NetworkStatsCollection(30);
+
+        // Create files for testing. Only the first and the third files should be counted,
+        // with total 26 (each char takes 2 bytes) bytes in the content.
+        final File statsDir = TestIoUtils.createTemporaryDirectory(getClass().getSimpleName());
+        write(statsDir, "uid_tag.1024-2048", "wanted");
+        write(statsDir, "uid_tag.1024-2048.backup", "");
+        write(statsDir, "uid_tag.2048-", "wanted2");
+        write(statsDir, "uid.2048-4096", "unwanted");
+        write(statsDir, "uid.2048-4096.backup", "unwanted2");
+
+        final NetworkStatsMetricsLogger.Dependencies deps =
+                mock(NetworkStatsMetricsLogger.Dependencies.class);
+        final NetworkStatsMetricsLogger logger = new NetworkStatsMetricsLogger(deps);
+        logger.logRecorderFileReading(PREFIX_UID_TAG, 678, statsDir, collection);
+        verify(deps).writeRecorderFileReadingStats(
+                NETWORK_STATS_RECORDER_FILE_OPERATED__RECORDER_PREFIX__PREFIX_UIDTAG,
+                1 /* readIndex */,
+                678 /* readLatencyMillis */,
+                2 /* fileCount */,
+                26 /* totalFileSize */,
+                0 /* keys */,
+                0 /* uids */,
+                0 /* totalHistorySize */
+        );
+    }
+
+    private void write(@NonNull File baseDir, @NonNull String name,
+                       @NonNull String value) throws IOException {
+        final DataOutputStream out = new DataOutputStream(
+                new FileOutputStream(new File(baseDir, name)));
+        out.writeChars(value);
+        out.close();
+    }
 }
diff --git a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
index 19216a7..9e6beb8 100644
--- a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
+++ b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
@@ -2231,7 +2231,7 @@
         return new NetworkStatsRecorder(new FileRotator(
                 directory, prefix, config.rotateAgeMillis, config.deleteAgeMillis),
                 observer, dropBox, prefix, config.bucketDuration, includeTags, wipeOnError,
-                false /* useFastDataInput */);
+                false /* useFastDataInput */, directory);
     }
 
     private NetworkStatsCollection getLegacyCollection(String prefix, boolean includeTags) {